Fast Optical Recording Circuit

This document presents technical details, hardware and software of a complete imaging system which uses a fast CCD sensor and a 41 Msample/s A/D converter to acquire full-frame 12 bit/pixel digitised images with a time resolution of 1.25 ms/image. The noise characteristics and the photon-capture capabilities of the system were analysed in detail. At the maximum readout rate, noise from the electronics amounted to ~300e-, without cooling.
Fast Optical Recording Circuit - schematic

Optical methods are interesting to physiologists and neuroscientists for several reasons. Of particular importance is the capability of recording simultaneously from multiple sites and the possibility to reach fast sampling rates. Therefore it is fundamental to develop imaging systems that, combining both features, achieve a high spatio-temporal resolution. In this respect, CCD sensors are well suited for detecting low-light level signals from fluorescent probes introduced into living cells. These devices possess high quantum efficiency for converting light into electrical signals that allow monitoring variations in the intracellular concentration of Ca2+ and other fundamental ions within the cell cytoplasm. Here we provide a detailed description of an imaging system based on a sensitive CCD sensor with high readout rate (16 MHz). Sensor’s output was digitised at 12 bit/pixel by customised electronics permitting image acquisition rates up to 800 frames/s with a full-frame resolution of 128´ 128 pixels.

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